Studies on B Group Vitamin Coenzyme-dependent Enzymes Related to Lysine Metabolism

Abstract

During the course of an investigation on microbial metabolism of lysine, my collaborator and I have found the occurrence of three kinds of new enzymes requiring NAD (P)^+ or FAD as a coenzyme : (1) meso-α, ε-diaminopimelate D-dehydrogenase in Bacillus sphaericus, which catalyzes the formation of meso-α, ε-diaminopimelate from L-α-amino-ε-ketopimelate, an intermediate of lysine biosynthesis in bacteria ; (2) L-lysine ε-dehydrogenase in Agrobacterium tumefaciens ; and (3) L-lysine α-oxidase in the aqueous extract of wheat bran culture of Trichoderma viride. These enzymes were purified to homogeneity and characterized. Furthermore, B_6 enzymes, L-lysine : α-ketoglutarate ε-aminotransferase and meso-α, ε-diaminopimelate decarboxylase which catalyzes the final step oflysine biosynthesis in bacteria have been studied with emphasis on the stereochemical mechanism of the enzyme reactions. Key Words : diaminopimelate dehydrogenase, lysine ε-dehydrogenase, lysine α-oxidase, stereochemistry of lysine ε-aminotransferase reaction, stereochemistry of diaminopimelate decarboxylase reaction.